freshwater clams in ponds do’s and don’ts
Freshwater clams are a good natural living filter media but it has a downside too. For example, its larvae will become a parasite to fish they will live on the fish gills and fins in addition if they became dead in your koi pond it will pollute your water.
Just unionid mussels attach to fish gills to complete their life cycle that is found in North America. There are other clams found in freshwater that does not require fish to attach to during the larval stage.
From my understanding, even the Unionid mussels would need to be very overpopulated in a pond to adversely affect the gills of fish located in the pond.
It would take a sizeable population of any freshwater bivalve to noticeably affect the water clarity on the typical garden pond. Notice the number of clams in the small aquarium in the video. Multiply this by the capacity (gallons) of your pond.
This is not to say that they would not be a welcome addition to the overall diversity of a pond.
If one is vigilant as to the source of these bivalves. They can harbor pathogenic organisms just as any fish or plant. Always utilize a reliable, responsible and established supplier. Sites such as Craig’s list and eBay should be avoided.